The present invention relates to an apparatus for operating a plurality of cycloconverters in a parallel fashion.
A cycloconverter is an apparatus to directly convert an ac power having a fixed frequency into an ac power having a different frequency. Such a cycloconverter has been widely used for a variable-voltage variable-frequency power supply for driving an ac motor. Particularly, it has been known that a cycloconverter of the circulating current type can set the upper limit of an output frequency f.sub.0 at a high value (an operation is possible at an output frequency about an input frequency f.sub.1) as disclosed in the Japanese Patent Publication Tokkaisho No. 60-28772, and the range of applications has been increasingly extended.
To overcome such drawbacks, a system described in the Japanese Patent Publication No. 59-14988 is proposed to connect a power factor compensating capacitor at the receiving-end of a cycloconverter to effect a control such that a lagging reactive power of the cycloconverter and a leading reactive power of the power compensating capacitor are cancelled with each other, thus allowing a power factor of a fundamental wave viewed from a power supply to always be unity.
However, various drawbacks have been pointed out in the art when an apparatus is provided with such a power factor compensating capacitor, or in regard to the relationship between the power factor compensating capacitor and the cycloconverter as understood from the following description.